It would be helpful to talk with your pediatrician about your son's diet to determine what you can do to relieve constipation. It sounds like you have been very supportive, and that approach is important. Punitive approaches to toileting issues can exacerbate problems like holding bowel movements. Be sure to let your son know that you are available to help him in the bathroom if he needs it. Some children have difficulty cleaning themselves and then make the problem worse trying to cover up the mess. Children sometimes have more success with flushable wipes that are available in most grocery stores. If necessary, you might try a reward system for bowel movements. This might encourage your son to have bowel movements on a more regular schedule. This approach would also encourage your son to draw posititive attention to his bowel movements rather than hiding and feeling ashamed. You could also require a clean bathroom for the reward, but offer to help in anyway he needed to keep the bathroom clean.
My son is also on the spectrum. If you think he needs the extra support for a while then go into the bathroom with him and support him through the process. You can always work at reducing that support again gradually as he gets back into the swing of things again. Or you could give him a board with visual or written instructions for him to follow through.
I agree that the moist wipes are alot easier than paper.
I think using laxatives for a while would be helpful so that he isn't fearful of a bowel movement. But don't rely on them too long as they can build up a tolerance to them and the bowel can become lazy.
Thank you so much for the insight. I have brought this to the attention of my sons pediatrician and she told me to give him childrens laxatives when he is constipated. Which I have and he is not struggling with the constipation any longer. I think now he is just dealing with the fear of it happening again. I will try the flushable wipes as well as encouraging him to keep the bathroom clean. I will keep you updated on the progress. Thank you again.